The present invention relates to a liquid crystal display apparatus capable displaying a high quality image by maintaining a high color purity in the range from a low luminance to a high luminance by reducing a tone change between grey scales or gradation levels and by optimizing a display image by adjusting a light source (back light) in accordance with a brightness of image signals.
The application field of a liquid crystal display has been expanded because it is thinner and lighter in weight than a cathode ray tube (CRT) having had a main trend of conventional display apparatuses and because of developments and advancements of angle of view enlarging technologies and moving image technologies.
As liquid crystal display apparatuses have expanded recently their use as monitors for desk-top type personal computers, monitors for printing and designing, and liquid crystal televisions, there are high needs for high color purity of red, green and blue and for color reproductivity of grey scales such as complexion. In the application to liquid crystal televisions, a high contrast ratio is required among other things, and not only a wide dynamic range of luminance but also color reproductivity from low luminance to high luminance is required. Liquid crystal display apparatuses are, however, associated with the problem that a color tone is likely to be changed with a change in luminance, i.e., a change in grey scale or gradation.
In order to achieve high luminance and high color purity, JP-A-2003-331608 describes the techniques of using a plurality type of light sources having different luminous colors and operating the light sources in two different modes, a color purity mode and a high luminance mode. As the techniques of improving moving image response characteristics and achieving a high luminance, JP-A-2003-140110 describes the configuration having a cold cathode fluorescent lamp and a light emitting diode array.